This invention relates to the field of slide chart manufacturing, and in particular to a method for manufacturing a slide chart from a unitary sheet blank using high speed, straight line, continuous motion gluing and folding machinery.
Slide charts have long been used as rapid and inexpensive calculation devices in a wide variety of fields. Generally, such slide charts are rectangular in shape, or circular in shape. This invention relates to the former type of slide chart.
Rectangular slide charts generally comprise two rectangular, outer faces, joined along both of their longitudinal edges, and a rectangular slide which is sandwiched in between the faces and the joined edges of the faces and which is permitted to slide within the confines of the resulting enclosure. Each of the faces and the slide is generally provided with printed material relating to the field to which the slide chart pertains. One or both of the faces are generally provided with openings through which material printed on the slide may be viewed. By aligning data contained on the slide or the faces of the slide chart, various calculations may be performed.
Such slide charts may be inexpensively manufactured, primarily from paper products, so that they may be widely distributed at a reasonable cost. Moreover, to further reduce costs of production, such slide charts are capable of formation from prefolded blanks into a finished product. An example of such a slide chart is described in U.S. Pat. No. 3,441,208, issued Apr. 29, 1969.
Although such slide charts are useful in many applications, the precision of the calculations they are capable of delivering is limited. In many, generally technical, applications the precision such a construction affords is insufficient for satisfactory results to be obtained using such a calculation device.
To improve the precision of the slide chart, workers in the art have constructed railed slide charts, similar in many respects to slide rules, which have found wide acceptance in the technical arts.
Non-railed slide charts are produced by folding two faces upon each other, sandwiching therebetween a slide forming the finished product. Irregularities in the folding and gluing of the faces has caused irregularities in the width of the slide chart produced. Consequently, the slide, in many cases, is permitted in skew slightly between the faces of the slide chart resulting in a lack of precision in calculations.
Railed slide charts are produced using a three-tiered construction. Comprising the three tiers are two faces, similar in construction to those of non-railed slide charts, and a slide which comprises two longitudinally extending rulings which form narrow strips along the longitudinal edges of the slide. In production, a first face is placed upon a surface with any data or other material printed thereon facing downward. Two narrow ribbons of glue are placed along the longitudinal edges of the first face, the width of the ribbons of glue being less than the width of the narrow strips of the slide. The slide is then placed over the first face and glued thereto along its edges. At this time care must be taken in aligning the edges of the slide with the edges of the face, to assure proper alignment of any data contained on the slide with the remainder of the slide chart. Two more ribbons of glue are then placed along the longitudinally extending strips of the slide. The second face is then placed over the slide and affixed thereto, taking care to assure proper alignment between the respective surfaces.
In manufacturing the slide of a railed slide chart, two scored lines are placed along the longitudinal edges of the slide to form the narrow strips previously mentioned. By scoring the slide for a distance less than the length of the slide the narrow strips are maintained in alignment with the slide prior to assembly of the slide chart. After assembly of the slide chart, the transverse edges of the slide chart are trimmed back a sufficient distance to free the center portion of the slide from the narrow strips of that slide. The center portion is then held between the narrow strips, which serve as rails along which the center portion may slide with improved precision. The skewing of the slide previously encountered is thereby substantially eliminated. The precision of the resulting calculation is greatly enhanced.
However, such increased precision is only obtained by increasing the complexity of manufacture of the device, causing substantial increases in the cost of producing such a slide chart. In particular, the alignment of the slide and the faces, which is generally performed by hand, presents a substantial increase in the cost of production.
This problem has been recognized by workers skilled in the art. U.S. Pat. No. 3,025,767, issued Mar. 20, 1959, illustrates a slide chart construction which attempts to overcome such alignment problems.
In that patent, a unitary slide chart blank is disclosed which is capable of being appropriately folded into a railed slide chart. Folds are located in a transverse orientation; strips of glue being located along the longitudinal edges of the blank. Alignment is enhanced by the folding process, rather than being entirely dependent upon the separate physical alignment of components.
Although such a blank enables costs of production to be reduced to a limited extent, workers in the art have continued to utilize the slower timed line manufacturing techniques to produce railed slide charts, thus limiting production speed. The folding and gluing steps required to produce a railed slide chart were not believed to be appropriate to the use of high speed folding techniques.
In particular, it was felt inappropriate to produce a folded product requiring the application of four ribbons of glue during its formation on high speed, straight line gluing and folding machinery, which had traditionally been used to form structures requiring only two ribbons, or sometimes only one ribbon, of glue. Consequently, the machinery used by workers in the art of high speed folding techniques was not believed to be applicable to the manufacture of a railed slide chart.
Accordingly, there exists a need to develop a railed slide chart which is capable of high speed alignment and production, to reduce the costs of production, without reducing or compromising the precision of such a slide chart and, therefore, its acceptance as a precision calculation device.